Explanation

• Atoms are made of subatomic particles: protons, neutrons, and electrons.
• Mass number represents the total number of heavy particles in nucleus.
• Only protons and neutrons contribute to atomic mass.

Last verified on 14-05-2026

Explanation

• Almost all the mass of an atom is concentrated in its nucleus.
• The nucleus contains protons and neutrons, which are much heavier than electrons.
• Electrons revolve around the nucleus but contribute very little to atomic mass.
• The nucleus is located at the center of the atom.
• Ernest Rutherford discovered the nucleus through the gold foil experiment in 1911.

Last verified on 09-05-2026

Explanation

• Our Solar System is located in the Orion Arm of the Milky Way galaxy.
• It including the Sun and eight planets.
• It consists of about 100–400 billion stars along with large amounts of gas and cosmic dust.

Additional information:

• The Milky Way is a spiral galaxy with a diameter of about 100,000 light-years.
• The nearest large galaxy to the Milky Way is Andromeda, located about 2.5 million light-years away.

Last verified on 11-03-2026

Explanation

• The Sun is a star at the center of our solar system with a surface temperature of about 6000 °C (Sun’s core is even hotter, ~15 million °C).
• It provides light and heat, essential for life on Earth.
• The Sun’s energy drives weather, photosynthesis, and climate.

Last verified on 18-03-2026

Explanation

• Every element is identified by the number of protons in its nucleus.
• This number determines the identity of the element.
• It is written as Z in chemistry.
• It is always equal to the number of electrons in a neutral atom.
• This is called the atomic number.

Last verified on 12-04-2026